1. Field of the Invention
This invention relates to an electronic device driven by a battery, and in particular to a portable computer or word processor in which the consumption of power required to operate power-consumption-variable components is controlled.
2. Discussion of the Background
The operating time period of a computer driven by a battery is determined by the amount of power consumed thereby since the maximum capacity of a battery is limited. The amount of power consumed by a computer varies depending upon factors such as the brightness of the display device employed, the frequency of the operation clock determining the speed of processing by the CPU, and the time periods during which power is supplied to various input/output devices. Power consumption will be high if the brightness of the display device is set to high level, the frequency of the operation clock is high, and power is supplied to each input/output device for long time periods. The greater the power consumption, the shorter the operating time period of the computer.
A battery-driven computer therefore has a power save function for prolonging its operating period to as long as possible. This function comprises a CPU sleep function, a magnetic disk (HDD) auto-power-off function, a display auto-power-off function, etc. Techniques relating to the power save function are disclosed in U.S. Pat. Nos. 4,907,183, 4,980,836, and 5,083,266.
In the case of the conventional power save functions, however, even if the user wishes to use the computer for a given time period, a power consumption amount corresponding to the time period desired cannot be set. In other words, although the user is aware that the operating time period of the computer will be prolonged by virtue of the power save functions, he cannot know at what degree each power save function is effected so as to use the computer for a desired time period.